1. Field of the Invention
The present invention relates to an ink jet printing head and a production thereof and in particular, to an ink jet printing head for discharging an ink droplet to a recording medium for image printing and a production method of the ink jet printing head.
2. Description of the Related Art
Conventionally, for example, this type of ink jet printing head is disclosed in Japanese Patent Publication No. A8-58089 [1].
FIG. 8 is a cross sectional view schematically showing a printing head identical to the one disclosed in Citation [1]. As shown here, the printing head, the conventional printing head includes: a nozzle plate 21, a pool plate 22, a supply perforation plate 23, a sealing plate 24, a pressure generating chamber 25, and a vibration plate 26 which are layered and to which an actuator 27 is mounted.
Moreover, in the nozzle plate 21, a nozzle 28 is formed for discharging ink. This nozzle 28 is connected to the pressure generating chamber 30 via a ink through hole 29 formed in the pool plate 22, the ink supply hole plate 23, and the sealing plate 24. Moreover, this pressure generating chamber 28 is connected to the ink pool 33 formed in the pool plate 22, via a supply communication path 31 formed in the sealing plate 24 and a ink supply hole 32 formed in the ink supply hole plate 23.
Thus, in the conventional method, a plurality of substrates having a nozzle 28 and the ink pool 33 are layered and an actuator 30 is attached to prepare an ink jet printing head. For attachment of the plurality of plates, adhesive is used.
When using adhesive for attachment between plates, there is a danger of adhesive clogging in the hole or groove such as a nozzle and nozzle communication hole.
In order to solve this problem, Japanese Patent Publication No. A5-330067 [2] discloses a technique to provide an escape groove in the vicinity of the nozzle so as to clear an unnecessary portion of the adhesive.
FIG. 9 is a perspective view of an ink jet printing head disclosed in Citation [2]. As shown here, a liquid adhesive 37 is applied as a thin film onto the surface of a plate 34 by way of xe2x80x98transferxe2x80x99 or xe2x80x98printingxe2x80x99, and a plate 38 is mounted thereon.
The plate 34 has on its surface an escape groove 36 for cleaning an unnecessary portion of the adhesive to suppress intrusion of the adhesive into the nozzle groove 35. Moreover, when such plates are multi-layered, the adhesive thickness values are identical.
However, it can not be said sufficient to provide an escape groove of the adhesive.
In general, in an ink jet printing head as shown in FIG. 8, the plate thickness differs depending on its purpose. For example, the vibration plate 26 should be thin enough to effectively transfer the vibration of the actuator 27 to the pressure generating chamber 30. Moreover, the ink plate 22 should be thick enough to assure a sufficient volume of the ink pool.
However, when an escape groove is to be provided as disclosed in Citation 2, in multi-layered plates having different thickness values, it is difficult to provide an escape groove in a thin plate. That is, it is impossible to form a groove having a depth greater than the thin plate thickness. It is also considered to increase width of the groove in the horizontal direction. However, if a groove has a wide width, there arise problems of plate strength and warp. Moreover, if a large groove is formed, the adhesion application area is decreased and the adhesive layer may not be uniform and have air bubbles (void).
The present invention intends to solve these problems. The object of the present invention is to provide an ink jet printing head and its production method capable of suppressing extrusion of adhesive into an ink flow path and increasing reliability and yield without causing irregularities or air bubbles (void) as well as reducing the production cost.
In order to achieve the object, claim 1 discloses an ink jet printing head comprising a plurality of substrates having a hole or groove which are attached to one another via an adhesive layer, wherein thickness of adhesive is adjusted according to a thinner substrate as a reference of two substrates to be attached to each other in such a way that the thickness of the adhesive becomes thinner as the reference substrate becomes thinner and thicker as the reference substrate becomes thicker.
Thus, according to the present invention, adhesive layer thickness is determined according to a thinner one of two adjacent substrates. Accordingly, it is possible to prevent extrusion of adhesive and clogging of a hole and groove provided on the respective substrates.
Claim 2 discloses an ink jet printing head as claimed in claim 1, wherein the plurality of substrates are constituted by: a nozzle plate having a nozzle for discharging ink; a pool plate having an ink pool and a first nozzle communication hole; a ink supply hole plate having a ink supply hole and a second nozzle communication hole; a chamber plate having a pressure generating chamber; and a vibration plate having an actuator for generating displacement, wherein the nozzle is connected to the pressure generating chamber via the first and the second ink through holes, and the pressure generating chamber is connected to the ink pool via the ink supply hole.
Moreover, claims 3 and 4 discloses an ink jet printing head as claimed in one of claim 1 and claim 2, wherein each of the adhesive layers is formed by an epoxy adhesive with a thickness 1 to 4 micrometers.
Thus, the present invention can further suppress extrusion of the adhesive. No air bubble (void) remains if the thickness is equal to or above 1 micrometer.
Moreover, claim 5 discloses a production method of an ink jet printing head comprising a plurality of substrates having a hole or groove which are attached to one another via an adhesive layer, wherein thickness of adhesive is adjusted according to a thinner substrate as a reference of two substrates to be attached to each other in such a way that the thickness of the adhesive becomes thinner as the reference substrate becomes thinner and thicker as the reference substrate becomes thicker.
Thus, according to the present invention, adhesive layer thickness is determined according to a thinner one of two adjacent substrates. Accordingly, it is possible to prevent extrusion of adhesive and clogging of a hole and groove provided on the respective substrates.
Moreover, claim 6 discloses an ink jet printing head production method as claimed in claim 5, wherein the plurality of substrates are constituted by: a nozzle plate having a nozzle for discharging ink; a pool plate having an ink pool and a first nozzle communication hole; a ink supply hole plate having a ink supply hole and a second nozzle communication hole; a chamber plate having a pressure generating chamber; and a vibration plate having an actuator for generating displacement; wherein the nozzle is connected to the pressure generating chamber via the first and the second ink through holes, and the pressure generating chamber is connected to the ink pool via the ink supply hole.
Moreover, Claim claims 7 and 8 discloses an ink jet printing head production method as claimed in one of claim 5 and 6, wherein each of the adhesive layers is formed by an epoxy adhesive with a thickness 1 to 4 micrometers.
Thus, the present invention can further suppress extrusion of adhesive and no irregularities or air bubbles (void) remain if the thickness is equal to or more than 1 micrometer.
Moreover, claim 9 discloses an ink jet printing head production method as claimed in claim 6, comprising steps of: applying adhesive onto the nozzle plate so as to form an adhesive layer and mounting the pool plate thereon; applying adhesive onto the pool plate so as to form an adhesive layer and mounting the ink supply hole plate thereon; applying adhesive onto the ink supply hole plate so as to form an adhesive layer and mounting the chamber plate thereon; and applying adhesive onto the pressure generating chamber plate so as to form an adhesive layer and mounting the vibration plate thereon; wherein the thickness values of the respective adhesive layers are adjusted in proportion to the respective thickness values of the substrates to be attached to the nozzle plate.
Thus, according to the present invention, when successively mounting plates onto the nozzle plate, the adhesive extrusion is caused mainly at the nozzle plate side. By defining the adhesive layer thickness according to the respective plate thickness values, it is possible to reduce the extrusion and increase the air tightness between the plates. When the plate thickness is small, the hole and groove formed in the plate have an inner wall of small area, and the adhesive layer thickness is also made small. Accordingly, it is possible to prevent extrusion of the adhesive into the hole and groove which may cause clogging.
Moreover, claim 10 discloses an ink jet printing head production method as claimed in claim 9, wherein each time a substrate is attached to the nozzle plate side, the substrate is pressed with a pressure proportional to thickness of the substrate.
When successively mounting plates on the nozzle plate, the adhesive extrusion is caused mainly at the nozzle plate side. Each of the plates is pressed with a force proportional to the plate thickness. This reduces extrusion and increases the air tightness between the plates. When the plate thickness is small, the hole and groove formed in the plate has a small area of inner wall. However, the pressure applied to the plate is proportional to the thickness. Thus, it is possible to prevent adhesive extrusion and accompanying clogging of the hole and groove formed in each plate.
Moreover, claim 11 discloses an ink jet printing head production method as claimed in 6, comprising steps of: applying adhesive onto the vibration plate to form an adhesive layer, and attaching the chamber plate onto the vibration plate; applying adhesive onto the chamber plate to form an adhesive layer, and attaching the ink supply hole plate onto the chamber plate; applying adhesive onto the ink supply hole plate to form an adhesive layer, and attaching the pool plate onto the ink supply hole plate; and applying adhesive onto the pool plate to form an adhesive layer, and attaching the nozzle plate onto the pool plate; wherein the respective adhesive layers have thickness values proportional to the thickness of the substrates attached to the vibration plate side.
When successively mounting plates on the vibration plate, the adhesive extrusion occurs mainly at the vibration plate side. Accordingly, by adjusting the adhesive layer thickness according to the plate thickness, it is possible to reduce the extrusion and increase the air tightness between the plates. When the plate thickness is small, the hole and groove formed in the plates also have a small area of inner wall. However, the adhesive layer thickness is also reduced. Accordingly, it is possible to prevent adhesive extrusion into the hole and groove, causing clogging.
Moreover, claim 12 discloses an ink jet printing head production method as claimed in claim 11, wherein each time a substrates is attached, the substrate is pressed with a pressure proportional to the thickness of the substrate.
When successively mounting plates on the vibration plate, the adhesive extrusion occurs mainly at the vibration plate side of the adhesive layer. By pressing a plate to be attached with a force roughly proportional to the plate thickness, it is possible to reduce the extrusion and increase the air tightness between the plates. When a plate thickness is small, the pressure applied to the plate is also made small. Accordingly, it is possible to prevent adhesive extrusion into the hole and groove, causing a clogging.
Moreover, claims 13-15 discloses an ink jet printing head production method as claimed in one of claims 5 to 12, wherein the adhesive layers in the vicinity of a hole or indentation are hardened in a time shorter than the other region of the adhesive layers.
Thus, according to the present invention, in the vicinity of a small hole, the adhesive is hardened before extrusion. Thus, adhesive extrusion can be prevented.
Thus, the present invention suppresses adhesive extrusion into the ink flow path and causes no irregularities or air bubble (void) in the adhesive layer. Consequently, the present invention increases reliability and yield as well as reduces the production cost.